Some people turn their homes into packrat middens. Such hoarding was thought to be a type of obsessive-compulsive disorder, OCD. But in the most recent diagnostic manual of psychological disorders, hoarding is proposed to be a unique condition—it’s now thought to be more about avoiding making decisions about possessions than a general obsession with them.

In a recent study, scientists compared the brain activity of hoarders with that of those with OCD, while the subjects were deciding whether to keep or toss their own junk mail and the junk mail of others.

Ownership did not affect the brain activity or choices of those with OCD. But the hoarders were different. Their decision-making brain circuit was quiet when contemplating others’ mail, but became overactive for decisions about their own mail. Not surprisingly, hoarders kept significantly more of their own mail than the OCD group did. The study is in the Archives of General Psychiatry.

Hoarders’ self-ratings of indecisiveness correlated with the amount of activity in brain circuits related to exaggerated perception of the risk of a wrong decision. The researchers suggest that hoarding behavior has its own specific symptoms and should be treated differently than OCD.